The present invention concerns a rotary crane, especially an offshore crane of the king post type with a pylon that can be permanently anchored to a base plate, platform, etc., a turntable mounted to revolve on the longitudinal axis of the pylon, a crane boom borne by the turntable and rotating gear for rotating the turntable on the pylon, where the upper support of the turntable includes a mount seated on an upper section of the pylon in such a manner that it can be rotated, which upper support has an axial support surface to brace axially against the pylon as well as a radial support surface to brace radially against the pylon and suspension means to suspend the turntable.
An offshore rotary crane of the king post type is known from, for example, U.S. Pat. No. 5,328,040 or U.S. Pat. No. 5,310,067. A boom that can luff on a horizontal axis is usually attached to the turntable, which boom can be pivoted by means of a supporting cable. Additionally, a lifting gear is usually positioned on the turntable or on the boom, which lifting gear has a lifting cable that runs over the peak of the boom for the purpose of lifting loads.
One problem with rotary cranes of this type concerns the rotating gear, with which the turntable together with the boom can be revolved on the pylon. As a consequence of play or distortions in the housing of the turntable on the pylon, for example as a result of wear or of manufacturing tolerances of the support, when loads are placed on the boom there may be tipping movements of the turntable with respect to the pylon. This can however cause damage to the rotating gear. In an extreme case, particularly when the bottom support of the turntable on the pylon is very worn, the corresponding forces are no longer absorbed by the support but rather by the rotating gear. The pinion drive is pressed too hard against the ring gear, so that the teeth of the ring gear or the drive pinion are damaged or the pinion shaft can break.
The present invention provides assistance here. The problem to be solved by the present invention is to create a rotary crane with an improved rotating gear that avoids the state-of-the-art disadvantages and further develops the state of the art in an advantageous manner.
According to the invention, this problem is solved by means of a rotary crane, especially an offshore crane, of the king post type, with a pylon that can be firmly anchored on a floor plate, platform, or the like, a turntable mounted to revolve around the pylon on its longitudinal axis, and rotating gear for rotating the turntable on the pylon, the rotating gear having a ring gear positioned on the pylon and a pinion drive that is connected with the turntable and which is in contact with the ring gear, the pinion drive being mounted on the turntable so that it can move radially relative to the ring gear, elastically forced against the ring gear. Preferred embodiments are described herein.
According to the invention, the rotating gear is designed in such manner that it can compensate for tipping movements of the turntable relative to the pylon caused by, for example, excessive support clearance. The pinion drive is mounted on the turntable in such manner as to move radially to the ring gear, so that when the turntable moves appropriately on the pylon the pinion drive yields and is not subjected to the corresponding forces. Advantageously the pinion drive is acted upon by restoring media that push the pinion drive back to the ring gear when the pinion drive is deflected, and force the pinion drive into its position in which it engages with the ring gear. The restoring media are supported appropriately on the turntable.
Especially, a spring device, preferably a compression spring, can be mounted on the turntable, which compression spring acts with restoring force on the ring gear. The spring device can be designed and positioned in such manner that in the starting position of the pinion drive the pinion drive is held in its starting position without initial tension, that is, the spring device exercises a force upon the pinion drive only when the pinion drive is pushed away from the pylon. Only when there is a torque transfer or a tipping movement of the turntable relative to the pylon, e.g. as a result of wear of the support, that is, when the drive pinion is pressed back, the spring becomes active and acts on the drive pinion with a spring power on the pylon. Appropriately, the restoring media are dimensioned in such manner that the pinion drive is always maintained in contact with the ring gear. The spring power exercised by the restoring media is preferably greater than the reaction power that occurs at the maximum drive torque of the pinion drive on the beveled tooth profile tending to push the pinion drive away from the ring gear. On the other hand, the restoring force is of course so small that upon appropriate movements by the turntable the pinion drive gives way in order to prevent its seizing or damage to it.
In principle, provision could be made to position only a portion of the drive pinion, especially the drive pinion meshing with the ring gear, movably on the turntable and to connect it with a drive motor by means of a drive element appropriate for permitting movement. Preferably, however, the pinion drive as a whole is mounted in such manner that it can move. The drive pinion meshing with the ring gear and the coordinated drive motor can form a unit that can move together in relation to the ring gear. According to a preferred embodiment of the invention, the drive pinion is positioned on a rocking arm that is mounted on a swivel axis on the turntable, which swivel axis is parallel to the longitudinal axis of the pylon. Preferably the swivel axis runs with its longitudinal axis essentially tangential to the perimeter direction of the pylon or the ring gear, so that the pinion drive mounted thereon swivels essentially radially away from the pylon and can be moved on the pylon when the rocking arm swivels on its swivel axis.
Preferably, for initial tension of the pinion drive, the spring device engages with the rocking arm and presses the rocking arm to the ring gear. The arrangement of pinion drive and spring device can theoretically vary. According to one embodiment of the invention, the pinion drive can be on one side and the contact point of the restoration medium can be on the other side of the swivel axis of the rocking arm. In this way an initial tension of the pinion drive against the ring gear can be created by means of a compression spring. According to one advantageous embodiment of the invention, however, the pinion drive and the contact point of the restoring medium are on the same side of the swivel axis. Especially, a compression spring can be caused to engage with the free end of the rocking arm, and the pinion drive can be positioned between the free end of the rocking arm and the rocking arm end that is mounted to swivel. This allows for a particularly compact design. In addition, a favorable mechanical advantage is achieved.
In a further development of the invention, the pinion drive is at a specified distance from the pylon or the ring gear. Advantageously, there is a support that is permanently connected with the pinion drive and which supports the pinion drive against its initial tension to the ring gear on the pylon. Appropriately the support tuns on a support surface different from the ring gear on the pylon.
In a further development of the invention, said support is on the rocking arm. The rocking arm is in continuous contact with the pylon. For example, the rocking arm can have a bearing surface that slides along the perimeter surface of the pylon. In a particularly preferred embodiment of the invention, on the free end of the rocking arm there is a support roller mounted to rotate on a rotary axis parallel to the swivel axis of the rocking arm. The initial tension of the spring device, whose working axis runs through the support roller, presses the support roller against the pylon so that the support roller can roll on its sleeve surface when the turntable is revolved relative to the pylon.
Theoretically, the pinion drive support can run directly on the top of the pylon. Preferably, however, a separate ring is attached to the pylon, which ring with its exterior perimeter surface forms the running surface for the support. On the one hand, this prevents the unavoidable wearing down of the running surface from leading to a weakening of the pylon. On the other hand, the ring can be manufactured from a suitable material independent of the material of the pylon. The ring can be metal and if necessary can be tempered. Even if the ring becomes worn, this does not lead to a weakening of the pylon.
In a further development of the invention, the rocking arm can have a passage recess in which the pinion drive rests and which is of such nature that there is a drive motor on one side of the rocking arm and a drive pinion connected with the drive motor on the opposite side of the rocking arm. The pinion is thus very close to the rocking arm, so that the engagement forces can exercise only limited tipping movements on the rocking arm. In an advantageous embodiment, the drive pinion, which engages with the ring gear, can be operated by means of a planetary gear of a rapidly turning hydraulic motor with low output torque.
In a further development of the invention, several pinion drives can be provided to engage with the ring gear positioned on the pylon. The pinion drives are distributed around the perimeter of the pylon.
In a preferred embodiment of the invention, the pinion drives are pressed back to the plane of symmetry of the rotary crane; they can be positioned in an acute-angle sector positioned centrally to the longitudinal center plane of the rotary crane, defined by the pylon and the boom of the crane. Preferably the pinion drives are on the front of the turntable, that is, on the side facing the boom.
Preferably the ring gear is also built separate from the pylon and is bolted to the pylon. This considerably simplifies the manufacturing of the ring gear. On the pylon there can be a flange-shaped bridge on which the ring gear rests and to which it is bolted.
In a particularly favorable embodiment of the invention, the ring gear is not ring-shaped or in a single piece. Rather, there is a multi-section ring gear that consists of several separate toothed segments. Said toothed segments are preferably removably attached to the pylon; especially they can be bolted to the pylon. According to a preferred embodiment, the toothed segments are positioned on a flange-shaped bridge to which they are bolted axially. Such design of the ring gear has particular advantages. Especially, the toothed segments can be precision-worked and tempered. Since they are not subsequently welded, there is no distortion. The high degree of precision facilitates a harmonious engagement of the drive, and less wear and tear. In addition, the multi-section design of the ring gear and the detachable connection of the toothed segments to the pylon makes replacement much easier when wear occurs. In contrast to a one-piece ring gear, which could be removed from the pylon, if at all, only after disassembly of the turntable from the pylon; individual toothed segments can be unbolted with relatively greater ease for removal or replacement